How To Converting Between IEnumVARIANT and java.util.Enumeration

MORE INFORMATION

Copy the source to a file named VarEnumeration.java and add it to your project. Include the following line to all your source files that use the VarEnumeration object:

   import VarEnumeration;
				

NOTE : the file name has to have the correct capitalization.

   // VarEnumeration.java
   // 
   // Written by Gregory W Singleton
   // of Microsoft Technical Support, Developer Support
   // Copyright (c) 1997 Microsoft Corporation. All rights reserved.
   // 
   // This class implements Enumeration to support Conversion from
   // IEnumVARIANT.
   // 
   // The constructor takes a reference to an existing IEnumVARIANT.

   import com.ms.com.*;
   import stdole2.*;
   import java.util.*;

   public class VarEnumeration implements Enumeration
   {
      private IEnumVARIANT enum = null;
      private Variant var = null;

      public VarEnumeration(IEnumVARIANT iev)
      {
         enum = iev;

         // Get first Element and store it
         nextElement();
      }

      public Object nextElement()
      {
         // Temporary variable to hold outgoing VARAINT
         Variant retval = var;

         // Create Variant to hold return from Next
         Variant tempVar = new Variant();
         tempVar.putEmpty();

         // Create Array of ints to hold number of returned items
         int[] numItems = new int[1];
         numItems[0] = 0;

         // Get next Item
         try
         {
            enum.Next(1, tempVar, numItems);
         }
         catch(Exception ex)
         {
            // enum.Next throws an exception when it cannot
            // return the amount of items requested
            numItems[0] = 0;
         }

         // Check to see if numItems == 0
         if(numItems[0] == 0)
            var = null; // If so, store null in var
         else
            var = tempVar; // If not, store it in var

         // Return previous VARAINT
         return retval;
      }

      public boolean hasMoreElements()
      {
         if(var == null)
            return false;
         else
            return true;
      }
   }
				

The class VarEnumeration has two public member functions that are used to implement the Enumeration interface. The first returns a Boolean if the collection has more elements:

   public boolean hasMoreElements()
				

The second returns the next Object from the collection:

   public Object nextElement()
				

This object will always be of type com.ms.com.Variant or null.

The following code illustrates using these functions. m_autoObject is a valid Automation object interface. The automation object exposes a method named "get_NewEnum()" of type com.ms.com.IUnknown.

   ...
   import stdole2.IEnumVARIANT;
   import com.ms.com.Variant;
   import java.util.Enumeration;
   import VarEnumeration;
   class TestEnum
   {
      ...
      public void tryTest
      {
         VarEnumeration varEnum = new
            VarEnumeration((IEnumVARIANT)m_autoObject.get_NewEnum());

         While(varEnum.hasMoreElements())
         {
            Variant var = (Variant)varEnum.nextElement();

            System.out.println("Variant Type: " + var.getvt());
         }
      }
      ...
   }
				

Once the above code is executed the automation objects collection is enumerated. A println call is made for each Variant returned showing its VT type.